LM117 3.3V PDF

When I remove the resistor and leave the capacitors, it does go back to 3. Email Required, but lm shown. Post as a guest Name. My question is, what if I use 2K and 3. In practice the change in Iadj is typically much smaller.

Author:Zololabar Telrajas
Language:English (Spanish)
Published (Last):7 October 2008
PDF File Size:3.49 Mb
ePub File Size:20.92 Mb
Price:Free* [*Free Regsitration Required]

Linear regulators inherently waste power; the power dissipated is the current passed multiplied by the voltage difference between input and output. A LM commonly requires a heat sink to prevent the operating temperature from rising too high.

For large voltage differences, the power lost as heat can ultimately be greater than that provided to the circuit. This is the tradeoff for using linear regulators, which are a simple way to provide a stable voltage with few additional components.

The alternative is to use a switching voltage regulator , which is usually more efficient, but has a larger footprint and requires a larger number of associated components. In packages with a heat-dissipating mounting tab, such as TO , the tab is connected internally to the output pin which may make it necessary to electrically isolate the tab or the heat sink from other parts of the application circuit. Failure to do this may cause the circuit to short.

Voltage regulator[ edit ] Schematic of LM in a typical voltage regulator configuration, including decoupling capacitors to address input noise and output transients. How the adjustment pin is connected determines the output voltage as follows.

If the adjustment pin is connected to ground the output pin delivers a regulated voltage of 1. Higher regulated voltages are obtained by connecting the adjustment pin to a resistive voltage divider between the output and ground.

The output current is that resulting from dropping the reference voltage across the resistor. Like the LM, each of the 78xx regulators is designed to adjust the output voltage until it is some fixed voltage above the adjustment pin which in this case is labelled " ground ".

Because of this, the error term in the formula cannot be ignored and the value of the low-side resistor becomes more critical. The LM is designed to compensate for these fluctuations internally, making such measures unnecessary.

The LM relates in the same way to the fixed 79xx regulators. These ICs are functional analogues of the LM


LM317 to output 3.3 Volts

Zuluzilkree What is the impact of increasing the resistors values but keeping the ratio the same? I am actually getting this Vout without using any capacitors or resistors. SO the ohm resistor shown for R1 would not meet the LM minimum load requirement worst case. By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. The LM datasheet specifies 10 mA max, 3. I can understand the usage of capacitors but not sure about the resistor used here. Make sure your capacitors are as close to the LDO as possible.


5V to 3.3V/1.8V Help Needed



LM317 LM117 区别


Related Articles